Loop limit in animation nodes?
There is no limit to the number of iterations in theory.

What makes your loop a bit more advanced is that you iterate through two lists at the same time. Normally you only want to do this when both lists have the same length because the addon works in the following way:

At first the loop will take the first element from both lists (Index 0). Then the second element from both lists, etc... This will continue until it reaches the last element of a list -> so the shortest list defines the number of iterations in a loop. The rest will be ignored.

The Evaluate Sound node outputs a float list with 10 elements in your example. 



The debug node in a loop always shows the last value that went into the node.

If you just want to move around all the objects you can simply remove the Float Iterator from the loop. Then each object should receive the transformation.

I guess you want to use the sound information in the loop with a different frequency for each object. The easiest way to archieve this is to use the Sound Equalizer template that ships with the addon: